The present invention is generally related to a method for ventilating electric machines, and, more particularly, to a method for improved distribution of cooling air to lower operating temperature of the machine.
Dynamo electric machines, such as motors, generators, etc., generate heat which must be removed efficiently to ensure long and economical operation of the machine. As shown in the exemplary prior art construction of FIG. 1, in an electric machine 10, such as a direct current (DC) traction motor, a suitable external blower 12 is commonly used to cool the machine by forcing a cooling fluid such as air from one end of the armature 14 of the machine through a plurality of venting passages therein, e.g., venting passage 16, to an opposite end. The armature 14 functions as a core and provides support for electrical coils 17 having end turns 19 projecting beyond the ends of the armature 14. The armature 14 is formed of a plurality of laminations (not shown) that are held together by an axial compressive load exerted on the armature 14 by a coil support 18 mounted on a spider structure 20, which is in turn mounted on the shaft 22 of the machine. In some embodiments, the spider 20 and coil support 18 may be formed as an integral unit. The coil support 18 includes a cooling passage 21 for passage of cooling fluid from the armature 14 away from the electrical coils 17 in the axial direction. Unfortunately, there may be regions of the end turns 19, e.g., the region proximate to flange 24, that are not cooled as well as other regions of the machine. This causes undesirable temperature rises in the machine and can result in overheating, and/or shorter insulation life. Either of such results would add burdensome costs to the operation of the machine. For this reason, there is a need for a method for cooling otherwise isolated parts of the machine.
It would be further desirable to provide a method that may be inexpensively provided to retrofit machines already deployed in the field without compromising the structural integrity of the machines, particularly the pre-loaded armature lamination stack, and without having to use complicated tooling equipment or labor intensive assembly.